Several different solid oxide fuel cell structural designs have been developed, including tubular, planar and monolithic designs, all of which are documented in the technical literature (see, for example, Q. M. Nguyen et al., “Science and Technology of Ceramic Fuel Cells”, Elsevier Science, January 1995). The tubular SOFC design originated from sealing problems associated with planar fuel cell stacks (see G. Hoogers, “Fuel Cell Technology Handbook”, CRC Press, August 2002). Numerous patents have issued to Siemens Westinghouse Power Corp., Orlando, Fla., disclosing the so-called air electrode supported (AES) technology (see, for example, U.S. Pat. No. 5,916,700 to Ruka, et al.; U.S. Pat. No. 5,993,985 to Borglum, and U.S. Pat. No. 6,379,485 also to Borglum).
Notwithstanding noteworthy technical achievements in the field of tubular SOFC, air electrode-supported tubular fuel cells still suffer from several disadvantages. For one, air electrode materials, such as lanthanum, strontium, manganite, etc., are costly often making the technology economically unattractive. In addition, air electrodes are made of ceramic materials and their mechanical strength and durability is often less than that of fuel electrodes made of cermets (i.e. ceramic and metal composites).
Fuel electrode-supported (FES) tubular SOFC have attracted new attention in the field in view of some improved economics (see U.S. Pat. No. 6,436,565 to Song, et al).
While AES and FES tubular designs have been modified structurally with both open ends and closed at one end few significant improvements have been made in the basic tubular configuration suggesting modifications to the internal structural features of tubular SOFC over conventional cylindrical configurations, as means for enhancing both the structural integrity and performance characteristics of this type of cell.
Accordingly, there is need for improved anodes for tubular SOFCs for enhancing structural support, durability and increasing surface area for optimizing electronic conductivity of the cell.